I need to change my marital status from Common Law to Single

You cannot change back to Single status for CRA tax purposes!

Once you file as Common-law, your Marital status can only be changed to Married, Separated or Widowed.

( and if you filed as Married, you can change to Separated, Divorced or Widowed).

In CRA terms you can never go back.

I have been in common law w a guy couple of years and filled out tax returns together. I have my own boy. In 2021 I ended the relationship and fill a tax single but we still living at the same address but no more not joining anything. Cos pay rent now very high so I still living here. If common law ended do I need to move out w a different address or not 

me and he only consider each shared room because the current rent is very high so I don't want to move but what effect does living in the same address have and how can it be proven that our relationship finished for change status in tax file